Almost all current production automobiles, as part of an overall occupant restraint system, are originally equipped with an array of inflatable restraint devices. The most common of such inflatable restraint devices is the airbag system, which is now more commonly referred to in the art as a Supplemental Restraint System (SRS), Air Cushion Restraint System (ACRS), or Supplemental Inflatable Restraint (SIR) system. Airbag devices are generally located in the passenger compartment of automotive vehicles, and act as a selectively deployable cushion capable of attenuating occupant kinetic energy. Most airbags are also designed to minimize inadvertent movement of the occupant to eliminate involuntary contact with the interior structure of the automobile.
Traditional airbag devices comprise an inflatable airbag module stored behind the vehicle instrument panel (e.g., for passenger-side airbags), mounted to the steering wheel hub (e.g., for driver-side airbags), or packaged within a vehicle seat assembly, side door trim, or headliner trim (e.g., for side-impact airbags). A plurality of sensors, such as accelerometers, wheel speed sensors, gyroscopes, brake pressure sensors, seat occupancy sensors, and similar devices, is strategically located throughout the automobile to detect the onset of a predetermined triggering event. A central airbag control unit (ACU) or sensing and diagnostic module (SDM) monitors the sensor(s), and responsively activates an inflation device, internally located in the airbag module, to produce a flow of inflating gas into an inflatable flexible cushion—i.e., the “airbag”, which is also located within the airbag module. The inflating gas causes the airbag cushion to be deployed into the vehicle passenger compartment, toward the vehicle occupant.
Many automotive vehicles are currently being designed with a supplemental inflatable restraint system located on a downward and forwardly inclined portion of the instrument panel, commonly identified as the “knee bolster”. The knee airbag, or “KAB”, can be extended so as to restrain the lower half of the occupant, engaging the knees and lower portions of the legs. During a predetermined triggering condition, the knee airbag cushion is inflated, traditionally passing or breaking through a rearward-facing surface of the knee bolster, in a manner similar to that described above with respect to traditional passenger airbag systems.
As an alternative to conventional KAB modules, inflatable knee bolsters have been developed to enhance vehicle occupant restraint in the event of sudden vehicle deceleration. Much like their conventional counterparts, the inflatable knee bolster is designed to increase the duration of occupant deceleration, and control occupant kinematics. Past inflatable knee bolster installations consist of an inflatable airbag cushion sandwiched between a movable, exterior impact surface, and a fixed-in-place interior surface.
The actuable knee bolster is arranged such that the bolster impact surface is movable from an undeployed position, where it sits flush against the instrument panel, to a deployed position, in which it extends rearward within the passenger compartment. When the inflator is triggered, the airbag cushion rapidly expands to move the impact surface a predetermined distance to the deployed position to intercept an occupant's knees early in the impact event. The inflatable knee bolster then deforms under load, absorbing kinetic energy and minimizing reaction forces. This provides the knees more time to decelerate to the vehicle's final velocity. The initial positioning of the bolster impact surface in a retracted, stored position allows more styling flexibility, and enhances ease of occupant ingress and egress.
During deployment, inflatable knee restraints, such inflatable knee bolsters are traditionally designed to expand in a direction perpendicular to their mounting angle. Since knee bolsters are angled downward, this results in a rearward and downward deployment trajectory. Due to the downward deployment direction, it may not be possible to optimally align the inflated restraint with the occupant.